So as to rearrange the printed circuits, normally parallelpiped housings are embodied with parallel slides equidistant by pairs, each receiving a card introduced through a cover of the housing and pushed as far as its connector so that the latter, placed upstream, is plugged into a connection plate fixed to the bottom of the housings. Secondly, orifices of the housing enable the cards to be cooled by an air current and possibly equipped with a perforated plate or grid for distributing this air.
When vibrations are possible, it is preferable to fix all the cards along the slides. To this effect, curved leaf springs are used, these springs being disposed in such a way as to press each card against its slide.
There also exist under-stress squeezing or clamping holding devices using screws. In, for example, the "LOK-TRAINER" brand known device sold by the BIRTCHER company, an open profile supports an undulated plate stressed by an end screw, thus pushing back the undulations against the card. This device considerably increases weight.
In extreme cases, the card is integrated into a metallic frame fixed by a set of screws into the housing. As the cards are then stacked and not slid, they are no longer independent and the unit then becomes extremely heavy.